Systems and methods of pressure drop control in fluid circuits through swirling flow mitigation

ABSTRACT

An injector with swirling flow mitigation includes an injector body defining a longitudinal axis. A fluid circuit is defined in the injector body and includes a plurality of flow channels defined in a cylindrical region around the longitudinal axis and being in fluid communication with an outlet orifice for passage of fluids out from the flow channels into a radial direction with respect to the longitudinal axis. A flow splitter is defined in each of the flow channels proximate the outlet orifice. Each flow splitter is configured and adapted to mitigate formation of swirling flow on fluids passing through the outlet orifice from the flow channels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 12/932,958, filed Mar. 10, 2011, which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to fuel injection, and more particularly to mitigation of swirling flow in fuel passages of fuel injectors.

2. Description of Related Art

Staged fuel injectors for gas turbine engines are well known in the art. They typically include a pilot fuel atomizer for use during engine ignition and low power engine operation, and at least one main fuel atomizer for use during high power engine operation. One difficulty associated with operating a staged fuel injector is that when the pilot fuel circuit is operating alone during low power operation, stagnant fuel located within the main fuel circuit can be susceptible to carbon formation or coking due to the temperatures associated with the operating environment. This can degrade engine performance over time.

To address these difficulties, efforts have been made to actively cool a staged fuel injector using the fuel flow from the pilot fuel circuit. U.S. Pat. No. 7,506,510, which is incorporated herein by reference in its entirety, discloses the use of active cooling to protect against carbon formation in the main fuel circuit of a staged airblast fuel injector. Increasingly, applications have emerged where the staging requirements include operation on pilot stage fuel at up to 60% of the maximum take-off thrust. This represents a substantial increase in the operational temperature for staged fuel injectors and tends to overheat the stagnant fuel in the un-staged main atomizer In order to provide the additional cooling needed for such applications, the pilot fuel circuits have become increasingly intricate, which can lead to significant pilot stage pressure drop.

Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for injectors that allow for increased pilot staging levels with improved pressure drop. There also remains a need in the art for such injectors that are easy to make and use. The present invention provides a solution for these problems.

SUMMARY OF THE INVENTION

The subject invention is directed to a new and useful fluid circuit. The fluid circuit includes a plurality of inlet flow channels configured for passage of fluids therethrough. The flow channels join one another at a junction with an outlet orifice. A flow splitter is defined in each of the flow channels proximate the outlet orifice. Each flow splitter is configured and adapted to mitigate formation of swirling flow on fluids passing through the outlet orifice from the flow channels.

In certain embodiments, there are two flow channels opposed to one another at the junction, however any suitable number of flow channels can be used. The flow splitter of each of the two flow channels can include an elongate flow splitter body dividing a portion of the respective flow channel into two branches and the two branches of each flow channel can be substantially equal to one another in flow area. The respective flow channel can have a flow area upstream of the two branches that is substantially equal to that of the two branches combined. The four branches can be dimensioned and configured to mitigate formation of swirling flow on fluids passing through the orifice even when one of the branches has a flow blockage.

It is contemplated that each flow splitter can be elongate in a longitudinal direction and can have a substantially rectangular cross-section normal to a longitudinal direction along the length thereof. Each flow channel can include a bend therein extending from the junction to a point upstream of the junction. The respective flow splitter of each of the flow channels can extend longitudinally through a majority of the bend in the respective flow channel Each flow splitter can be spaced apart from the outlet orifice by a distance in a range of about 0.0 times to about 1.0 times the width of the outlet orifice. Each flow splitter can extend in a direction away from the outlet orifice to a point upstream of a bend in the respective channel It is also contemplated that the outlet orifice can have a shape that substantially deviates from a perfect circle.

The invention also provides an injector having an injector body that defines a longitudinal axis. A fluid circuit is defined in the injector body. The fluid circuit includes a flow channel defined in a cylindrical region around the longitudinal axis. The fluid circuit is in fluid communication with an orifice for passage of fluids out from the flow channel into a radial direction with respect to the longitudinal axis. A flow splitter as described above is defined in the flow channel proximate the orifice. The fluid circuit can include first and second flow channels opposed to one another at a junction with the orifice, as described above. The flow splitter can be integral with the injector body.

The invention also provides a staged fuel injector. The staged fuel injector includes a main fuel circuit for delivering fuel to a main fuel atomizer. The main fuel atomizer includes a radially outer prefilmer and a radially inner fuel swirler, wherein portions of the main fuel circuit are formed in the prefilmer. A pilot fuel circuit is included for delivering fuel to a pilot fuel atomizer which is located radially inward of the main fuel atomizer. The pilot fuel circuit includes a plurality of flow channels defined in the prefilmer and the fuel swirler. The pilot fuel circuit also includes a conduit for conveying fuel from the flow channels to the pilot fuel atomizer. The conduit is in fluid communication with the flow channels at an orifice. A flow splitter is defined in each of the flow channels proximate the orifice. Each flow splitter is configured and adapted to mitigate formation of swirling flow on fluids passing through the orifice from the flow channels into the conduit.

In certain embodiments, a portion of each flow channel of the pilot fuel circuit defined in the radially outer prefilmer is in fluid communication with a portion of the respective flow channel defined in the radially inner fuel swirler by way of a radial passage. The radial passage can be circular or can have a non-circular cross-sectional shape selected from the group consisting of pill-shaped, oblong, ovoid, or any other suitable non-circular shape. The flow channel upstream of the radial passage can include a flow splitter configured and adapted to mitigate formation of swirling flow on fluids passing through the radial passage. The radially outer prefilmer, the radially inner fuel swirler, and the flow splitters can be integral with one another. It is also contemplated that the flow splitters can be integral with the radially inner fuel swirler, which can be joined together with the radially outer prefilmer at a braze joint. If a given channel is wide enough, two or more flow splitters can be included in the channel side by side without departing from the spirit and scope of the invention.

These and other features of the systems and methods of the subject invention will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the devices and methods of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:

FIG. 1 is a perspective view of an exemplary embodiment of a staged fuel injector constructed in accordance with the present invention, showing the spray outlet;

FIG. 2 is a perspective view of the injector of FIG. 1, showing the inlet end portion of the injector;

FIG. 3 is a cross-sectional side elevation view of the injector of FIG. 1, showing the fuel and air circuits for the main and pilot fuel stages;

FIG. 4A is a schematic view of the main prefilmer portion of the injector of FIG. 1, showing the fuel passages formed in the radially outer surface thereof;

FIG. 4B is a schematic view of the main fuel swirler portion of the injector of FIG. 1, showing the fuel passages formed in the radially outer surface thereof, including the flow splitters;

FIG. 5A is a perspective view of the main prefilmer of FIG. 4A, showing the fuel passages formed in the radially outer surface thereof;

FIG. 5B is a perspective view of the main fuel swirler of FIG. 4B, showing the fuel passages and flow splitters formed therein;

FIG. 6 is a cut away perspective view of a portion of the injector of FIG. 1, showing schematically the swirling flow resulting when there are no flow splitters proximate the bore leading to the pilot fuel atomizer;

FIG. 7 is a cut away perspective view of a portion of the injector of FIG. 1, showing the flow splitters, wherein the flow into the bore is shown schematically wherein the flow splitters mitigate the formation of swirling flows proximate the bore leading to the pilot fuel atomizer;

FIG. 8 is a cut away perspective view of the portion of the injector of FIG. 7, schematically showing the effects of a total blockage in one of the four branches of the fuel channels adjacent the flow splitters;

FIG. 9 is a perspective view of a portion of the prefilmer of FIG. 5A, showing the pill-shaped radial ports for passage of fuel into the fuel channels of the fuel swirler; and

FIG. 10 is a cut away perspective view of a portion of another exemplary embodiment of a staged fuel injector constructed in accordance with the subject invention, showing a single flow splitter extending over the bore leading to the pilot fuel atomizer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject invention. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of an injector in accordance with the invention is shown in FIG. 1 and is designated generally by reference character 10. Other embodiments of injectors in accordance with the invention, or aspects thereof, are provided in FIGS. 2-10, as will be described. The systems and methods of the invention can be used to reduce pressure loss by mitigating swirling flow in flow channels, such as in fuel injectors for gas turbine engines.

Referring now to FIG. 1, fuel injector 10 is adapted and configured for delivering fuel to the combustion chamber of a gas turbine engine. Fuel injector 10 is generally referred to as a staged fuel injector in that it includes a pilot fuel circuit, which typically operates during engine ignition and at low engine power and a main fuel circuit, which typically operates at high engine power (e.g., at take-off and cruise) and is typically staged off at lower power operation.

Fuel injector 10 includes a generally cylindrical nozzle body 12, which depends from an elongated feed arm 14, and defines a longitudinal axis A. In operation, main and pilot fuel is delivered into nozzle body 12 through concentric fuel feed tubes. As shown in FIG. 3, these feed tubes include an inner/main fuel feed tube 15 and an outer/pilot fuel feed tube 17 located within the feed arm 14. Although not depicted herein, it is envisioned that the fuel feed tubes could be enclosed within an elongated shroud or protective strut extending from a fuel fitting to the nozzle body.

Referring now to FIG. 2, at the same time fuel is delivered to nozzle body 12 through feed arm 14, pressurized combustor discharge air is directed into the inlet end 19 of nozzle body 12 and directed through a series of main and pilot air circuits or passages, which are shown in FIG. 3. The air flowing through the main and pilot air circuits interacts with the main and pilot fuel flows from feed arm 14. That interaction facilitates the atomization of the main and pilot fuel issued from the outlet end 21 of nozzle body 12 and into the combustion chamber of the gas turbine engine.

Referring now to FIG. 3, nozzle body 12 includes a main fuel atomizer 25 that has an outer air cap 16 and a main outer air swirler 18. A main outer air circuit 20 is defined between the outer air cap 16 and the outer air swirler 18. Swirl vanes 22 are provided within the main outer air circuit 20, depending from outer air swirler 18, to impart an angular component of swirl to the pressurized combustor air flowing therethrough.

An outer fuel prefilmer 24 is positioned radially inward of the outer air swirler 18 and a main fuel swirler 26 is positioned radially inward of the prefilmer 24. Prefilmer 24 has a diverging prefilming surface at the nozzle opening. As described in more detail herein below with reference to FIGS. 5A and 5B, portions of the main and pilot fuel circuits are defined in the outer diametrical surfaces 24 a and 26 a of the prefilmer 24 and main fuel swirler 26, respectively.

With continuing reference to FIG. 3, the main fuel circuit receives fuel from the inner feed tube 15 and delivers that fuel into an annular spin chamber 28 located at the aft end of the main fuel atomizer The main fuel atomizer further includes a main inner air circuit 30 defined between the main fuel swirler 26 and a converging pilot air cap 32. Swirl vanes 34 are provided within main inner air circuit 30, depending from pilot air cap 32, to impart an angular component of swirl to the pressurized combustor air flowing therethrough. In operation, swirling air flowing from main outer air circuit 20 and main inner air circuit 30 impinge upon the fuel issuing from spin chamber 28, to promote atomization of the fuel.

Nozzle body 12 further includes an axially located pilot fuel atomizer 35 that includes the converging pilot air cap 32 and a pilot outer air swirler 36. A pilot outer air circuit 38 is defined between pilot air cap 32 and pilot outer air swirler 36. Swirl vanes 40 are provided within pilot outer air circuit 38, depending from air swirler 36, to impart an angular component of swirl to the air flowing therethrough. A pilot fuel swirler 42, shown here by way of example, as a pressure swirl atomizer, is coaxially disposed within the pilot outer air swirler 36. The pilot fuel swirler 42 receives fuel from the pilot fuel circuit by way of the inner pilot fuel conduit 76 in support flange 78. Pilot fuel conduit 76 is oriented radially, or perpendicularly with respect to longitudinal axis A.

Nozzle body 12 includes a tube mounting section 12 a and an atomizer mounting section 12 b of reduced outer diameter. Tube mounting section 12 a includes radially projecting mounting appendage that defines a primary fuel bowl for receiving concentric fuel tubes 15 and 17 of feed arm 14. A central main bore 52 extends from the fuel bowl for communicating with inner/main fuel tube 15 to deliver fuel to the main fuel circuit. Dual pilot fuel bores (not shown, but see, e.g., bores 54 a and 54 b in FIG. 6 of the above-referenced U.S. Pat. No. 7,506,510) communicate with and extend from the fuel bowl for delivering pilot/cooling fuel from outer/pilot fuel tube 17 to the pilot fuel circuit.

Referring now to FIGS. 4A and 4B, the outer diametrical surface 24 a of outer prefilmer 24 and the outer diametrical surface 26 a of main fuel swirler 26 include channels or grooves that faun portions of the main and pilot fuel circuits or pathways. FIG. 4A is a schematic representation of prefilmer 24 as if unrolled from its cylindrical form shown in FIG. 5A to show the fluid pathways schematically. Outer pilot fuel circuit 60 includes two generally J-shaped fuel circuit half-sections 60 a and 60 b and a central section 60 c formed in surface 24 a. Main fuel circuit 70 is also formed in outer diametrical surface 24 a of outer prefilmer 24. Main fuel circuit 70 is located forward, i.e., toward inlet end 19 shown in FIG. 2, of the two pilot fuel circuit half-sections 60 a and 60 b and consists of a central fuel distribution section 70 a which distributes fuel to four feed channels 70 b that terminate in twelve (12) axially extending exit sections 70 c. As discussed in the above-referenced U.S. patent application Ser. No. 12/932,958, the exit sections 70 c provide fuel to exit ports that feed into spin chamber 28, which is shown in FIG. 3. The outer pilot fuel circuit half-sections 60 a and 60 b receive fuel from the pilot fuel tube 17 (see FIG. 3) via the central section 60 c. A portion of the pilot fuel provided by the fuel tube 17 is directed to an inner pilot fuel circuit 62, which is described below with reference to FIGS. 4B and 5B, through port 63. Main fuel circuit 70 receives fuel from central fuel bore 52, by way of inner fuel tube 15, shown in FIG. 3.

Referring now to FIGS. 4B and 5B, inner pilot fuel circuit 62 is formed in the outer diametrical surface 26 a of fuel swirler 26. FIG. 4B is a schematic representation of swirler 26 as if unrolled from its cylindrical form shown in FIG. 5B to show the fluid pathways schematically. The inner pilot fuel circuit 62 includes a central section 62 c, which receives the pilot fuel from port 63 (see FIG. 4A), and commonly terminating U-shaped channels 62 a and 62 b. In addition to receiving fuel from the central section 62 c, the channels 62 a and 62 b are fed fuel from respective radial transfer ports 64 a and 64 b (see FIG. 4A) associated with outer pilot fuel circuit half-sections 60 a and 60 b, respectively. Fuel from the channels 62 a and 62 b is directed to the pilot fuel swirler 42, shown in FIG. 3, through an inner pilot fuel bore 67 formed in pilot atomizer support flange 78, which depends from the interior surface of fuel swirler 26. As described in the above-referenced U.S. patent application Ser. No. 12/932,958, fuel traveling through the outer and inner pilot fuel circuits 60 and 62 is directed into thermal contact with the outer main fuel circuit 70, en route to the pilot fuel atomizer 35 located along the axis A of nozzle body 12. Each flow channel 62 a and 62 b includes a bend 82 therein extending from the junction with bore 67 to a point upstream of the junction. Each of channels 62 a and 62 b includes a respective flow splitter 80 in the respective bend 82 for swirling flow mitigation, as described in greater detail below with respect to FIG. 7. While described in the exemplary context of having two channels at the junction, those skilled in the art will readily appreciate that any suitable number of channels can be included without departing from the spirit and scope of the invention.

Referring now to FIG. 6, prefilmer 24 is joined outboard of swirler 26 by any suitable technique such as brazing. In this manner, the fuel channels formed in the outer surfaces 24 a and 26 a are formed in a cylindrical region around the axis A shown in FIG. 1. It is also contemplated that a prefilmer and swirler could be formed as an single integral component, such as by additive manufacturing techniques as described in the above-referenced U.S. patent application Ser. No. 12/932,958.

It has been discovered in conjunction with the subject invention that in fluid circuits having a junction of flow channels such as the junction of channels 62 a and 62 b with inner pilot fuel bore 67, a swirling flow can result at the junction. FIG. 6 shows a fluid circuit, i.e., inner pilot fuel circuit 62, with two opposed channels 62 a and 62 b which are joined with a conduit 76 at a junction proximate inner pilot fuel bore 67. The flow arrows in FIG. 6 schematically indicate the swirling flow generated by this arrangement of channels, orifice, and conduit. FIG. 6 shows flow channels 62 a and 62 b without flow splitters 80 in order to describe the swirling flow effect.

Without wishing to be bound by theory, it is believed that for internal flow of liquids or gases, as the flow transitions from a channel to a hole or tube, which may be oriented perpendicular to the general incoming flow path, a swirling flow field can be established in the flow as it passes through the hole or tube. Relatively minor fluctuations or imbalances in the flow from channels meeting a hole or tube give rise to the swirling flow draining into the hole or tube. The swirling flow is stable, and it is believed that depending on the upstream fluctuations and/or imbalances, the swirl direction can vary to be clockwise or counter clockwise from circuit to circuit. Such swirling flows have been demonstrated with test hardware as well as with CFD modeling in conjunction with the subject invention.

While there may be applications where swirling flow behavior is desirable, such as for increasing heat transfer or for a cyclone particle separator, the swirling flow indicated in FIG. 6 has the detrimental effect of lowering the effective flow number for the fluid circuit, effectively reducing the available flow area through conduit 76 (where flow number is mass flow rate in pounds-per-hour divided by the square-root of the pressure-drop in pounds-per-square-inch). Swirling flow creates a loss in useful (or useable) energy due to flow in non-desired directions, i.e. flow around a conduit rather than through the conduit, and ultimately acts like a blockage to reduce flow number. This reduced flow number translates into pressure drop that exceeds predictions based on standard design techniques, i.e., standard design techniques do not account for the pressure drop due to the swirling flow effects described above. This swirl-related pressure drop becomes particularly significant in applications where a relatively high flow is required in the fluid circuit, such as in pilot stages of fuel injectors operating at 60% of the maximum take-off thrust with pilot stage fuel only.

Referring now to FIG. 7, in order to mitigate the swirling flow phenomenon described above, fluid circuits constructed in accordance with the subject invention include flow splitters 80 defined in each of the flow channels 62 a and 62 b proximate the respective outlet orifice, e.g., bore 67 leading to conduit 76. Each flow splitter 80 is configured and adapted to mitigate formation of swirling flow on fluids passing through the outlet orifice from the flow channels. As indicated schematically by flow arrows in FIG. 7, each flow splitter 80 splits the flow in its respective channel going around the respective bend 82, reducing variation in pressure, velocity, and mass flow-rate in fluids approaching bore 67. In certain applications, flow splitters such as flow splitters 80 can help avoid flow separations around sharp turns in their respective flow channel. The effect of flow splitters 80 is that a strong swirl or vortex does not form at the junction with bore 67. In short, flow splitters 80 reduce or eliminate swirling flow and the related pressure drop, effectively providing a higher flow number than would otherwise be provided.

With continued reference to FIG. 7, each flow splitter 80 includes an elongate flow splitter body dividing a portion of the respective flow channel into two branches 84 a and 84 b. The two branches 84 a and 84 b are substantially equal to one another in flow area, and the respective flow channel 62 a or 62 b has a flow area upstream of branches 84 a and 84 b that is substantially equal to that of the two branches 84 a and 84 b combined.

Each flow splitter 80 is elongate in a longitudinal direction around bend 82 and has a substantially rectangular cross-section normal to the longitudinal direction along the length thereof. This can be accomplished by machining branches 84 a and 84 b out of surface 26 a, for example. A gap, e.g., 0.010 inches or more, can be provided between the flow splitters 80 and the inner surface of prefilmer 24, which can be advantageous in preventing a braze fillet from forming on the top of the splitters 80. The respective flow splitter 80 of each of the flow channels 62 a and 62 b extends longitudinally through a majority of the respective bend 82.

Each flow splitter 80 should be spaced apart from the respective outlet orifice, e.g., bore 67, by a distance in a range of about 0.0 times to about 1.0 times the width of the outlet orifice, i.e., from no distance to about one outlet orifice diameter's distance, with no distance/spacing being the most effective for swirl mitigation. Swirling flow can be mitigated with distances outside this range, but generally, the effects of mitigating unwanted swirl diminish as this distance increases. This distance should be maintained to prevent the flows from the two branches 84 a and 84 b from fully rejoining into a single flow that could generate a swirling flow before passing into bore 67.

On the opposite end, namely the far end from bore 67, each flow splitter 80 extends in a direction away from the outlet orifice to a distance that depends on the particular application. It is important that the upstream extent of flow splitters 80 be located upstream of or very near to where the channel turns from a straight run. In other words, flow splitters 80 should extend upstream of their respective bend 82 for the most effective swirl mitigation. The upstream end of a flow splitter 80 can be located downstream of the start of a bend 82, however the effectiveness is generally diminished. In applications where there is no bend 82 prior to a bore such as bore 67, a nominal flow splitter length of about twice the channel width should be used. Generally, the longer the flow splitter length, the more effective the flow splitter at mitigating unwanted swirl. In short, the flow splitters 80 should extend upstream far enough to split the flow at a point upstream of any potential swirl effects forming.

Referring now to FIG. 8, branches 84 a and 84 b are dimensioned and configured to mitigate formation of swirling flow on fluids passing through the orifice even when flow is not even among the four branches 84 a and 84 b. This is the case even if one of the branches has a total flow blockage. Flow blockage 86 is shown in FIG. 8 completely blocking off flow through branch 84 b of channel 62 b. However, it has been demonstrated in conjunction with the subject invention that the remaining three branches 84 a and 84 b of channels 62 a and 62 b do not form a strongly swirling flow at bore 67. Rather, the flows from the three unblocked branches 84 a and 84 b enter conduit 76 as indicated schematically by flow arrows in FIG. 8. Thus even if one of the four branches 84 a or 84 b becomes completely blocked off, the total pilot fuel circuit flow can still be ample for a given application, and the overall flow is still better than if no flow splitters 80 are provided. Blockages such as blockage 86 can arise during the manufacture of an injector, such as by excess braze flowing into one of the branches 84 a or 84 b when joining fuel swirler 26 to prefilmer 24, or can result from debris or impurities in the fuel, or the like.

Referring now to FIG. 9, another manner of reducing swirling flow at a junction between a flow channel and an orifice in accordance with the subject invention involves the shape of the orifice itself. FIG. 9 shows a portion of prefilmer 24 diametrically opposite bore 67 shown in FIGS. 7 and 8. The ends of the generally J-shaped fuel circuit half-sections 60 a and 60 b include radial transfer ports 64 a and 64 b, also shown in FIG. 4A, for allowing fuel to flow radially inward into channels 62 a and 62 b, shown in FIGS. 4B and 5B. There is a potential to form a swirling flow at ports 64 a and 64 b, much as described above, even though the flow junction includes only one channel with a perpendicular port or orifice, rather than two opposed channels. However, ports 64 a and 64 b are elongate and have a pill shape, rather than being simple circular bores. This elongate shape reduces swirling flow and therefore reduces pressure drop across the ports 64 a and 64 b. It is also contemplated that in accordance with the subject invention an outlet orifice, such as ports 64 a and 64 b, can have any suitable shape that substantially deviates from a perfect circle, such as oblong or ovoid. Generally, the larger the aspect ratio of the non-circular orifice shape, the more effective the swirl mitigation. In other words, the more eccentric an elliptical orifice is, or the larger the width to length ratio is for a pill shaped orifice, for example, the more effective the orifice is at mitigating swirl. It is also contemplated that flow splitters such as flow splitters 80 could be positioned upstream of ports 64 a and 64 b to mitigate swirling flow, in which case the ports 64 a and 64 b could be circular or non-circular as described above. Additionally, it is also contemplated that in addition to or in lieu of flow splitters 80, bore 67 and/or conduit 76 of FIG. 7 could be non-circular as described above to mitigate swirling flow therein. In short, non-circular orifice/tube shapes and/or flow splitters can be used to mitigate swirling flow where flow channels have ports or radial passages therethrough, such as in radial ports 64 a and 64 b or as in bore 67 and conduit 76. Moreover, while described herein in the exemplary context of radially inward flow through a radial orifice, those skilled in the art will readily appreciate that the flow mitigating features described herein can also be used for radially outward flow through a radial orifice.

With reference now to FIG. 10, a portion of another exemplary embodiment of an injector 90 includes an integral swirler and prefilmer component 94, much like prefilmer 24 and swirler 26 described above, but formed as a single component. This can be accomplished, for example, by additive manufacturing techniques such as those described in the above-referenced U.S. patent application Ser. No. 12/932,958. Since component 94 is formed as a single, integral component, flow splitter 88 can extend across bore 96. Flow splitter 88 is generally similar to flow splitters 80 described above, but is a single elongate structure rather than two separate structures each stopping short of bore 67 as shown in FIG. 7. This configuration enhances the maintenance of separate flows in each branch of channels 92 all the way to bore 96.

While described above in the exemplary context of having a single flow splitter dividing a flow channel into two branches, those skilled in the art will readily appreciate that any suitable number of flow splitters can be included, dividing a flow channel into any suitable number of branches without departing from the spirit and scope of the invention. It is possible to gain at least some swirl mitigation benefits, even if only one of two opposed flow channels includes one or more flow splitters. Additionally, in applications where there is only one flow channel, rather than two opposed flow channels, leading up to a bore, one or more flow splitters in the channel can provide significant swirl mitigation, without departing from the spirit and scope of the invention.

The exemplary embodiments described above show applications where flow channels have bores or conduits joining them at a perpendicular orientation, however those skilled in the art will readily appreciate that oblique angles for the bores or conduits can also be used without departing from the spirit and scope of the invention. Moreover, while described in the exemplary context of fuel flow in fuel injectors, those skilled in the art will readily appreciate that the features of the invention described above can readily be used in any other suitable application without departing from the spirit and scope of the invention.

The methods and apparatus described above are useful in reducing swirling flow and therefore pressure drop in flow geometries such as those described above. This can be particularly advantageous in applications such as pilot fuel circuits for fuel injectors in gas turbine engines where fuel staging requirements include pilot only operation at up to 60% or more of the maximum take-off thrust. Other advantages for fuel injector applications include the reduced likelihood of coking because of lower fuel temperatures that result from shorter fuel residence time in the fuel channels due to mitigation of regions of recirculating flow.

The methods and systems of the present invention, as described above and shown in the drawings, provide for fluid circuits, such as in injectors, with superior properties including improved pressure drop through swirling flow mitigation. While the apparatus and methods of the subject invention have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject invention. 

1. A fluid circuit comprising: a) a plurality of inlet flow channels configured for passage of fluids therethrough, wherein the flow channels join one another at a junction with an outlet orifice; and b) a flow splitter defined in each of the flow channels proximate the outlet orifice, each flow splitter being configured and adapted to mitigate formation of swirling flow on fluids passing through the outlet orifice from the flow channels.
 2. A fluid circuit as recited in claim 1, wherein there are two flow channels opposed to one another at the junction, and wherein the flow splitter of each of the two flow channels includes an elongate flow splitter body dividing a portion of the respective flow channel into two branches.
 3. A fluid circuit as recited in claim 1, wherein there are two flow channels opposed to one another at the junction, wherein the flow splitter of each of the two flow channels includes an elongate flow splitter body dividing a portion of the respective flow channel into two branches, and wherein the two branches of each flow channel are substantially equal to one another in flow area.
 4. A fluid circuit as recited in claim 1, wherein the flow splitter of each of the flow channels includes an elongate flow splitter body dividing a portion of the respective flow channel into two branches, wherein the respective flow channel has a flow area upstream of the two branches that is substantially equal to that of the two branches combined.
 5. A fluid circuit as recited in claim 1, wherein each flow splitter is elongate in a longitudinal direction and has a substantially rectangular cross-section normal to a longitudinal direction along the length thereof.
 6. A fluid circuit as recited in claim 1, wherein there are two flow channels opposed to one another at the junction, and wherein the flow splitter of each of the two flow channels includes an elongate flow splitter body dividing a portion of the respective flow channel into two branches, and wherein the four branches are dimensioned and configured to mitigate formation of swirling flow on fluids passing through the orifice even when one of the branches has a flow blockage.
 7. A fluid circuit as recited in claim 1, wherein there are two flow channels opposed to one another at the junction, wherein each flow channel includes a bend therein extending from the junction to a point upstream of the junction, and wherein the respective flow splitter of each of the two flow channels extends longitudinally through a majority of the bend in the respective flow channel.
 8. A fluid circuit as recited in claim 1, wherein each flow splitter is spaced apart from the outlet orifice by a distance in a range of about 0.0 times to about 1.0 times the width of the outlet orifice.
 9. A fluid circuit as recited in claim 1, wherein each flow splitter extends in a direction away from the outlet orifice to a point upstream of a bend in the respective channel.
 10. A fluid circuit as recited in claim 1, wherein the outlet orifice has a shape that substantially deviates from a perfect circle.
 11. An injector comprising: a) an injector body defining a longitudinal axis; b) a fluid circuit defined in the injector body, the fluid circuit including a flow channel defined in a cylindrical region around the longitudinal axis and being in fluid communication with an orifice for passage of fluids out from the flow channel into a radial direction with respect to the longitudinal axis; and c) a flow splitter defined in the flow channel proximate the orifice, the flow splitter being configured and adapted to mitigate formation of swirling flow on fluids passing through the orifice from the flow channel.
 12. An injector as recited in claim 11, wherein the flow channel is a first flow channel and the flow splitter is a first flow splitter, wherein the fluid circuit includes a second flow channel defined in the cylindrical region around the longitudinal axis of the injector body, wherein a second flow splitter is defined in the second flow channel proximate the orifice, and wherein the first and second flow channels oppose one another at a junction with the orifice, and wherein the flow splitter of each of the two flow channels includes an elongate flow splitter body dividing a portion of the respective flow channel into two branches.
 13. An injector as recited in claim 11, wherein the flow channel is a first flow channel and the flow splitter is a first flow splitter, wherein the fluid circuit includes a second flow channel defined in the cylindrical region around the longitudinal axis of the injector body, wherein a second flow splitter is defined in the second flow channel proximate the orifice, wherein the first and second flow channels oppose one another at a junction with the orifice, wherein each flow channel includes a bend therein extending from the junction to a point upstream of the junction, and wherein the respective flow splitter of each of the two flow channels extends longitudinally through a majority of the bend in the respective flow channel.
 14. An injector as recited in claim 11, wherein the flow splitter is integral with the injector body.
 15. A staged fuel injector comprising: a) a main fuel circuit for delivering fuel to a main fuel atomizer, the main fuel atomizer including a radially outer prefilmer and a radially inner fuel swirler, wherein portions of the main fuel circuit are formed in the prefilmer; b) a pilot fuel circuit for delivering fuel to a pilot fuel atomizer which is located radially inward of the main fuel atomizer, wherein the pilot fuel circuit includes a plurality of flow channels defined in the prefilmer and the fuel swirler, the pilot fuel circuit further including a conduit for conveying fuel from the flow channels to the pilot fuel atomizer, wherein the conduit is in fluid communication with the flow channels at an orifice; and c) a flow splitter defined in each of the flow channels proximate the orifice, each flow splitter being configured and adapted to mitigate formation of swirling flow on fluids passing through the orifice from the flow channels into the conduit.
 16. A staged fuel injector as recited in claim 15, wherein a portion of each flow channel of the pilot fuel circuit defined in the radially outer prefilmer is in fluid communication with a portion of the respective flow channel defined in the radially inner fuel swirler by way of a radial passage, wherein the flow channel upstream of the radial passage includes a flow splitter configured and adapted to mitigate formation of swirling flow on fluids passing through the radial passage.
 17. A staged fuel injector as recited in claim 15, wherein the radially outer prefilmer, the radially inner fuel swirler, and the flow splitters are integral with one another.
 18. A staged fuel injector as recited in claim 15, wherein the flow splitters are integral with the radially inner fuel swirler, and wherein the radially inner fuel swirler and the radially outer prefilmer are joined together at a braze joint.
 19. A staged fuel injector as recited in claim 15, wherein there are two flow channels of the pilot fuel circuit defined in the radially inner fuel swirler that are opposed to one another at a junction with the conduit to the pilot fuel atomizer, and wherein the flow splitter of each of the two flow channels includes an elongate flow splitter body dividing a portion of the respective flow channel into two branches. 20-21. (canceled) 